Issue 697 - Show API error when calling .complete on Anthropic client

lib/langchain/llm/anthropic.rb

@@ -81,7 +81,10 @@ def complete(
       parameters[:metadata] = metadata if metadata
       parameters[:stream] = stream if stream
 
-      response = client.complete(parameters: parameters)
+      response = with_api_error_handling do
+        client.complete(parameters: parameters)
+      end
+
       Langchain::LLM::AnthropicResponse.new(response)
     end
 
@@ -114,6 +117,15 @@ def chat(params = {})
       Langchain::LLM::AnthropicResponse.new(response)
     end
 
+    def with_api_error_handling
+      response = yield
+      return if response.empty?
+
+      raise Langchain::LLM::ApiError.new "Anthropic API error: #{response.dig("error", "message")}" if response&.dig("error")
+
+      response
+    end
+
     private
 
     def set_extra_headers!

lib/langchain/llm/base.rb

@@ -8,6 +8,7 @@ class ApiError < StandardError; end
   # Langchain.rb provides a common interface to interact with all supported LLMs:
   #
   # - {Langchain::LLM::AI21}
+  # - {Langchain::LLM::Anthropic}
   # - {Langchain::LLM::Azure}
   # - {Langchain::LLM::Cohere}
   # - {Langchain::LLM::GooglePalm}

spec/fixtures/llm/anthropic/error.json

@@ -0,0 +1,7 @@
+{
+  "type": "error",
+  "error": {
+    "type": "invalid_request_error",
+    "message": "The request is invalid. Please check the request and try again."
+  }
+}

spec/langchain/llm/anthropic_spec.rb

@@ -30,6 +30,25 @@
         expect(subject.complete(prompt: completion).model).to eq("claude-2.1")
       end
     end
+
+    context "with failed API call" do
+      let(:fixture) { File.read("spec/fixtures/llm/anthropic/error.json") }
+
+      before do
+        allow(subject.client).to receive(:complete)
+          .with(parameters: {
+            model: described_class::DEFAULTS[:completion_model_name],
+            prompt: completion,
+            temperature: described_class::DEFAULTS[:temperature],
+            max_tokens_to_sample: described_class::DEFAULTS[:max_tokens_to_sample]
+          })
+          .and_return(JSON.parse(fixture))
+      end
+
+      it "raises an error" do
+        expect { subject.complete(prompt: completion) }.to raise_error(Langchain::LLM::ApiError, "Anthropic API error: The request is invalid. Please check the request and try again.")
+      end
+    end
   end
 
   describe "#chat" do